Biotransformation of chromium (Cr-VI to Cr III) from tannery effluent using bacteria and fungi

Chromium, a priority pollutant is well known for its mutagenicity, carcinogenicity and teratogenicity in humans, animals and plants. Extensive use of chromium in industries such as leather tanning, stainless-steel production, electroplating and wood preservatives have resulted in extensive chromium contaminated soil and ground water. Microorganisms are involved in the removal of toxic wastes, both in the natural environment and in controlled treatment systems. The present study was undertaken to optimize the chromium reduction capabilities of microbes isolated from the tannery effluents of Dindigul district. About 68 bacterial and 23 fungal isolates were identified based on their microscopic and macroscopic features. The screening was done on minimal salt media incorporated with potassium dichromate. The Bacillus amyloliquefaciens CRB36 strain showed the maximum chromium reduction activity when compared to other bacterial and fungal species isolated in this study. The optimization of chromium reduction was done using various physico-chemical parameters. In the optimization study, the best condition for the reduction of toxic form of chromium was achieved when starch and peptone were supplied as carbon and nitrogen sources at an optimum pH of 7.0 with an incubation temperature of 30°C. Bioremediation is the most promising, eco-friendly and cost effective technology widely used now a days for detoxification of toxic industrial pollutants in soil and water.